"The package of 18 amendments would abolish the office of prime minister and give the president the authority to draft the budget, declare a state of emergency and issue decrees overseeing ministries without parliamentary approval."
[www.reuters.com]

Polling stations across the country closed by 5:00 p.m. (10.00 a.m. ET) and results were expected to start coming in within hours. Stations in eastern Turkey, which opened an hour earlier, were closed at 4:00 p.m. (1300 GMT).

Opinion polls have shown a narrow lead for a "Yes" vote, which would replace Turkey's parliamentary democracy with an all-powerful presidency and may see Erdogan in office until at least 2029.

The outcome will shape Turkey's strained relations with the European Union. The NATO member state has curbed the flow of migrants - mainly refugees from wars in Syria and Iraq - into the bloc but Erdogan says he may review the deal after the vote.

A crowd chanted "Recep Tayyip Erdogan" and applauded as the president shook hands and greeted people after voting in a school near his home in Istanbul. His staff handed out toys for children in the crowd.

"God willing I believe our people will decide to open the path to much more rapid development," Erdogan said in the polling station after casting his vote.

"I believe in my people's democratic common sense."

Some 55 million people were eligible to vote at 167,140 polling stations. Turkish voters abroad have already cast their ballots.